By Jesse Prinz

It is astonishing how quickly nature has gone into retreat. Until
five or ten years ago, the dominant story was that our genes were our
fate. Our fixed endowments in the shape of unlearned capacities, innate
modules, biologically hard-wired dispositions and evolutionary
inheritances from the savannah dominated the scene, with culture and
history relegated to mere bit players.

The first cracks in the consensus appeared with the realisation that
genes work differently in different environments. For example, it was
discovered that if rats were separated into two groups, one of which
received maternal care and love while the other did not, parts of the
brain grew better in the former group and they were less likely to flood
themselves with stress hormones such as cortisol. So, if you want a
laid-back rat, mother it properly. Epigenetic factors began to muscle in
on the DNA monopoly.

Of course, in human beings we already knew - didn't we? - that such
environmental factors affected children's characters. And it didn't take
much guessing to suppose that it did this by making some difference to
their brains. But somehow it took the addition of brain scans and
neurophysiological and endocrinal data from rats to make such beliefs
respectable again, so that anthropology could begin to claw back ground
from biology.

Jesse Prinz, a philosopher at the City University of New York, has
written an excellent guide to the current state of play. Prinz is
admirably cautious about the nature-nurture dispute, which always has to
come down to matters of detail and degree. His interest is in human
flexibility, although he freely admits that "we need very sophisticated
biological resources to be as flexible as we are". Nevertheless, it is
clear where his sympathies lie. Early in the book he tells us that only
"a tiny fraction of articles in psychology journals take culture into
consideration". So it is time to redress the balance, and Prinz does it
with insight, learning and above all a wonderful eye for the weaknesses
in biological reductionist arguments.

Prinz lays out his case by first considering the difference between
colour vision, which is a natural capacity with a well-understood
biological underpinning, and the capacity to play baseball, which
requires putting together a number of general capacities in a way that
takes a great deal of nurture to develop. The question, then, is the
size of the innate inventory of capacities, rules, dispositions and
tendencies, shaped over time by evolution, and themselves constituting
adaptations to older environments. Are they large, computationally fixed
and relatively inflexible, like colour vision? Or is it more a matter
of general-purpose abilities (running, balancing, throwing, remembering)
exquisitely tuned by culture and learning into one form or another,
like baseball?

In the former camp we have evolutionary psychologists, nativists and
those who like a picture of the mind as a kind of Swiss Army knife: an
aggregation of dedicated modules rigidly shaped by evolution. In the
latter camp, we have those who stress general purpose learning
capacities, which in one environment might enable you to become a
cricketer, but in another a baseball player. At the dawn of the
scientific revolution, the philosophical ancestors of the first group
were rationalists such as Descartes and Leibniz, who saw the mind as
ready-furnished by God with a nice array of innate capacities. The
ancestors of the second group were the empiricists, who thought that we
needed no such interior designer. Experience could do the furnishing all
by itself.

Ever since the work of Noam Chomsky in the middle of the 20th
century, our capacities with language have been one of the major
battlegrounds. The trump card of Chomsky and his followers is the
"poverty of stimulus" argument. This alleges that empiricism cannot
account for language learning. We learn too much, too quickly, making
too few mistakes, extrapolating what we learn too accurately, for this
to be the result of any general empirical learning process. Out of all
the myriad possible patterns linguistic systems might implement, the
infant almost miraculously picks up the right one, with far too little
experience or correction to explain the unfolding capacities. Only a few
theorists have dared to challenge this Chomskyan consensus. And
Chomskyans are certainly right that the infant cannot be doing it by
consciously formulating rules, since even expert linguists often cannot
do as much.

Prinz makes a strong, detailed case that statistical learning, the
poster child of empiricism, can account for everything we know about
language learning. Children do not just imitate, they extrapolate. They
try things out. They take patterns they hear and extend them
experimentally. They are unconsciously nudged into shape by the
regularities in the data sets to which they are exposed. And this makes
sense: the brain is designed to pick up on patterns in the environment,
whether they indicate edibility in food, change in the weather, the
passage of a predator, the way to cook a squirrel, or the acceptability
of a new sentence. Instead of arriving packed with innate universal
grammars, we come ready to pick up whatever the world is going to throw
at us. The quicker we learn its ins and outs, the better.

The example may sound dry, but there is a vital humanistic lesson in
the book. It has been all to easy to cite "innate" differences as
justifications of the social status quo, when too often it is the social
status quo that generates the illusion of the innate differences. For
example, the belief that girls are naturally girlish and boys naturally
boyish ignores the ubiquitous pressures to conform to the acceptable
pattern, starting well before birth and reinforced throughout life.
Prinz writes well about this, too. Similar remarks apply, of course, to
those who, themselves belonging to the supposedly superior group, put
different IQ scores or arithmetical or musical ability down to
differences of race, before reflecting on the social and cultural
environments of those who are being compared.

Prinz's final chapter is about sex, but I shall not spoil the plot.
Suffice it to say that we are not naturally polygamous, or monogamous,
or anything else, except perhaps naturally inclined to bend the truth on
questionnaires. "Those who want to understand our preferences will
learn more from history books than from chimpanzee troops in the Gombe,"
Prinz tells us. "[B]iology can help explain why we are more likely to
flirt with a person than a potato, but that's just where the story
begins."

From start to finish this book is a fine, balanced, enormously
learned and informative blast on the trumpet of common sense and humane
understanding. The story is largely optimistic but also reminds us that
when things go wrong around us, we are all capable of going wrong with
them.

Simon Blackburn is Bertrand Russell professor of Philosophy at
Cambridge. His most recent book is "Practical Tortoise Raising and Other
Philosophical Essays" (Oxford University Press, £25)